# solving equation using mathematical induction

• October 29th 2012, 11:17 AM
jakobjakob
solving trigonometric equation using mathematical induction
Prove that this is true for every n. (n is an element of natural numbers)

cos(n*pi) = (-1)^n

I would very much appreciate your help, thank you.
• October 29th 2012, 11:31 AM
johnsomeone
Re: solving trigonometric equation using mathematical induction
$\text{Use: } \cos((n+1) \pi ) = \cos(n\pi + \pi) = \cos(n\pi)\cos(\pi) - \sin(n\pi)\sin(\pi), \text{ and continue on from there.}$
• October 29th 2012, 12:02 PM
jakobjakob
Re: solving trigonometric equation using mathematical induction